Why being bilingual helps keep your brain fit
​Most people in the world speak more than one language, suggesting the human brain evolved to work in multiple tongues. If so, asks Gaia Vince, are those who speak only one language missing out?

Multilingualism has been shown to have many social, psychological and lifestyle advantages. Moreover, researchers are finding a swathe of health benefits from speaking more than one language, including faster stroke recovery and delayed onset of dementia.
Could it be that the human brain evolved to be multilingual – that those who speak only one language are not exploiting their full potential? And in a world that is losing languages faster than ever – at the current rate of one a fortnight, half our languages will be extinct by the end of the century – what will happen if the current rich diversity of languages disappears and most of us end up speaking only one?

There were warnings that bilingual children would be confused by two languages, have lower intelligence, low self-esteem, behave in deviant ways, develop a split personality and even become schizophrenic. It is a view that persisted until very recently, discouraging many immigrant parents from using their own mother tongue to speak to their children, for instance. This is in spite of a a 1962 experiment, ignored for decades, which showed that bilingual children did better than monolinguals in both verbal and non-verbal intelligence tests.
However, research in the last decade by neurologists, psychologists and linguists, using the latest brain-imaging tools, is revealing a swathe of cognitive benefits for bilinguals. It’s all to do with how our ever-flexible minds learn to multitask.

In fact, says cognitive neuropsychologist Jubin Abutalebi, at the University of San Raffaele in Milan, it is possible to distinguish bilingual people from monolinguals simply by looking at scans of their brains. “Bilingual people have significantly more grey matter than monolinguals in their anterior cingulate cortex, and that is because they are using it so much more often,” he says. The ACC is like a cognitive muscle, he adds: the more you use it, the stronger, bigger and more flexible it gets.
Bilinguals, it turns out, exercise their executive control all the time because their two languages are constantly competing for attention. Brain-imaging studies show that when a bilingual person is speaking in one language, their ACC is continually suppressing the urge to use words and grammar from their other language. Not only that, but their mind is always making a judgement about when and how to use the target language. For example, bilinguals rarely get confused between languages, but they may introduce the odd word or sentence of the other language if the person they are talking to also knows it.
“My mother tongue is Polish but my wife is Spanish so I also speak Spanish, and we live in Edinburgh so we also speak English,” says Thomas Bak. “When I am talking to my wife in English, I will sometimes use Spanish words, but I never accidentally use Polish. And when I am speaking to my wife’s mother in Spanish, I never accidentally introduce English words because she doesn’t understand them. It’s not something I have to think about, it’s automatic, but my executive system is working very hard to inhibit the other languages.”

This article first appeared on Mosaic and is republished here under a Creative Commons licence.